For David Millier

Started Feb 4, 2013 | Discussions thread
richard stone
Senior MemberPosts: 1,580
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Re: I'll get my coat ;-)
In reply to DMillier, Feb 7, 2013

DMillier wrote:

The purpose of "handicapping", as you call it, is to:

- prevent a rectangular panel punched full of holes rendering as a series of diagonal stripey moire patterns.

- And to prevent a thin line like a strand of wire or a handrail rendering like it was made of lego bricks instead of as a smooth tube.

- Or to make a regular tiled roof render with a horizontal tile pattern instead of an imaginary diagonal one.

- Or to make a geometrically shaped pattern actually render consistently instead of fading in an out like a diffraction pattern.

- Or to render all the rivets along the side of a bridge instead of having every fourth one mysteriously disappear.

- Or to have a receding line of fence posts render with consistent spacing rather going double width, then quadruple width as you get further away.

- In other words to have a consistent, predictably rendered image that doesn't do weird things with patterns.

Aliasing does sometimes add the appearance of extra detail, it can help create a sense of acutance but it also introduces weird gibberish into the shot.

Of course this is subject dependent. Architectural subjects seem to me to be the worst subjects for provoking the bad behaviour.

Oh, as you have never actually seen a properly anti-aliased Foveon image, how can you know for sure that it wouldn't be stunningly beautiful?

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No, and neither have you.

But I will assume, based on what I imagine would be a realistic development path for the Foveon sensors, that someone, at some time, and for some good reasons, did in fact experiment with such a filter on the Foveon sensor. It seems to me unrealistic to assume otherwise.

And the result for Sigma/Foveon seems to have been more in the negative than in the positive, obviously. And again, obviously, three other major companies, all known for quality and innovation, Nikon and Leica and Fuji, have now made concerted efforts to avoid the need for, and eliminate, the AA filter, on high end cameras. Sigma seems to have been out in front on that issue.

So I remain puzzled about your unusual and continuing concern with this "issue." If you wish to use an AA filter on the SD1, the answer is obvious, in a crude way: use a somewhat soft and blurry lens. It seems that doing so somewhat defeats the over-all purpose of the camera and, as pointed out above, the stair-stepping problem ("jaggies") that seems to so trouble you is not really a true product of aliasing. However, such a test might answer some of your questions. Perhaps someone can supply this information using the SD1M and a somewhat lower quality lens.

Richard

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